PREFACE
Although these lectures were delivered without the aid of a manuscript, they have been printed substantially as they were spoken, making allowance for the exigencies of an experimental lecture. Here and there I have introduced a little new matter to give some measure of completeness to the exposition. My object was to interest and instruct, and an appeal was made to experiment wherever that was possible. It is no doubt difficult to present the facts of science in a book with the same vividness as when they are demonstrated by experiment; but I have endeavoured, by introducing numerous illustrations, to suggest to the mind what was actually done at the lecture. The delivery of these lectures was a pleasure to myself, as, with the resources of the Royal Institution, I saw certain physiological phenomena more clearly than is possible
